The emission of carbon dioxide (CO2) has been rising for the last several decades as a result of increasing use of fossil fuel by different sectors of industry. In 2011, the emissions of CO2 into the atmosphere reached over 34.000 million metric tons. In 2015, the CO2 concentration in the atmosphere increased to 401 parts per million (ppm), which is 110 ppm more than at the start of the industrial revolution and contributing to more than 60% of the global warming. As a consequence, global temperature has increased ˜1° C. in the last 50 years. If the use of fossil fuels continues at this or increasing rate over the next 50 years, the CO2 concentration in the atmosphere could reach 580 ppm, causing significant global effects on living organisms and ecosystems.
Conventional technologies for CO2 capture and sequestration from blast furnace gasses (BFG) are based on either physical or chemical methods. In physical methods, CO2 is absorbed by a solid or liquid under various pressures and temperatures and is released by the absorbents upon decompression and/or heating. For example, physical absorption methods include pressure swing absorption, and vacuum pressure swing absorption.
While physical absorption requires higher CO2 partial pressures, chemical absorption is appropriate for CO2 capture from gases with low CO2 partial pressures. The chemical absorption methods are based on chemical reactions between the absorbent and CO2. Organic amines are the most common absorbents, including monoethanolamine (MEA), monoethanolamine/piperazine mix, and sterically hindered primary amines. CO2 removal by absorption and regeneration with aqueous ammonia solution is a mature and widely used method. Amine absorption, however, is costly and energy intensive due to the relatively low CO2 absorption capacity (0.4 tCO2 t−1MEA). Using amine systems to capture 90% of CO2 emitted from a flue gas of fossil-fuel power plant could cost up to 30% of the electricity generated by the plant. MEA solvent based absorbents have also been criticized because of their low absorption capacity, corrosive nature, and fast degradation of absorption capacity in the presence of exhaust gas.
Adsorption and CO2 membranes are two other technologies that have been developed. For example, CO2 selective membranes provide a viable energy-saving alternative for CO2 separation from flue or fuel gas because membranes do not require any phase transformation. However, this technology is not considered as a suitable solution due to the selectivity and stability of the membranes, the structure and permeation properties of the membranes, and the transport mechanism applied in the membranes.
Siderite is a commercial mineral and has many applications such as a source of iron in the steel industry, raw material in cement industry, hydrogen production, refining of ferrosilicon, and shale oil production. In nature, carbonate minerals are part of various rocks mainly represented by the quaternary system FeCO3—MgCO3—CaCO3—MnCO3. Natural samples of iron carbonate show different amounts of substitutions of Mg, Ca, Mn for Fe in the lattice, which suggests that pure siderite seldom occurs. Natural siderite forms complete series of solid solutions with magnesium and manganese carbonates, while a wide miscibility gap has been reported between iron and calcium carbonates. Solubility of Ca2+ in siderite does not exceed 10 mol. % at 550° C., while calcite (CaCO3) can contain up to 20 mol. % of Fe2+ at the same temperature.
The thermal decomposition of siderite is a very important issue mainly in the processing of oil shales or in the combustion of coals. The mechanism of the thermal decomposition of siderite is complicated and depends both on its composition and experimental conditions. There is a remarkable difference in the thermal decomposition behavior of natural and synthetic siderite. For example, the decomposition temperature of synthetic siderite is approximately 200 K below the decomposition temperature of the natural sample. Formation of solid solutions between FeCO3 and other metal carbonates increases the decomposition temperature of natural siderite samples compared to synthetic ones. Temperature, atmosphere, microstructure, heating rate are experimental parameters that determine phase composition of siderite decarbonation products.
Therefore, there is a need to develop novel systems and methods for capturing CO2, reducing its emission from, for example, steel industry and separating CO2 from fossil fuel. There is also a need for siderite synthesis and decomposition, in particular, at ambient conditions.